Textile machine with improved pattern control system

ABSTRACT

A knitting machine for forming a fabric includes a device which is driven at a predetermined speed to blend at least two colors of fibers together to form the fabric. First and second feed units driven by first and second motors, respectively, feed the fibers into the device at rates corresponding to the speeds of the motors. A tachometer driven by the device produces a first voltage which is proportional to the speed of the device and a potentiometer energized by that voltage is adjustable to produce a second voltage which is a selectable fraction of the first voltage. Means responsive to the second voltage causes the first motor to run at a speed proportional to that voltage and a combining device receiving the first and second voltages produces a third voltage equal to the differences of the first two voltages. Means responsive to the third voltage energizes the second motor to run at a speed proportional to the third voltage so the combined amount of fiber being fed into the device remains constant while the individual rates at which the different colors of fibers are fed into the device may be varied to produce a pattern in the fabric.

United States Patent [1 1 [111 3,91 1,696

Buckholtz et al. Oct. 14, 1975 [5 TEXTILE MACHINE WITH INIPROVED [57] ABSTRACT PATTERN CONTROL SYSTEM Inventors: Eric A. Buckholtz, Janesville;

Werner M. Randell, Milton, both of Wis.

Assignee: Norwood Mills, Inc., Janesville, Wis.

Filed: June 3, 1974 Appl. No.: 475,644

US. Cl. 66/9 B; 19/l45.7

Primary ExaminerWm. Carter Reynolds Attorney, Agent, or Firm-Wolfe, Hubbard, Leydig, Voit & Osann, Ltd.

A knitting machine for forming a fabric includes a device which is driven at a predetermined speed to blend at least two colors of fibers together to form the fabric. First and second feed units driven by first and second motors, respectively, feed the fibers into the device at rates corresponding to the speeds of the motors. A tachometer driven by the device produces a first voltage which is proportional to the speed of the device and a potentiometer energized by that voltage is adjustable to produce a second voltage which is a selectable fraction of the first voltage. Means responsive to the second voltage causes the first motor to run at a speed proportional to that voltage and a combining device receiving the first and second voltages produces a third voltage equal to the differences of the first two voltages. Means responsive to the third voltage energizes the second motor to run at a speed proportional to the third voltage so the combined amount of fiber being fed into the device remains constant while the individual rates at which the different colors of fibers are fed into the device may be varied to produce a pattern in the fabric.

18 Claims, 10 Drawing Figures 1,4 I 0 y, I

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l a J? //a L I mar/4'! IfltI/JI Juarez" -o l f/PAJ/V/(fl I US. Patent Oct. 14, 1975 Sheet 1 of4 3,911,696

US. Patent Oct. 14, 1975 Sheet 2 0'54 3,911,696

US. Patent Oct. 14, 1975 I Sheet 3 of 4 Sheet 4 of 4 US. Patent 0m. 14, 1975 TEXTILE MACHINE WITH IIVIPROVED PATTERN CONTROL SYSTEM BACKGROUND OF THE INVENTION This invention relates generally to a textile machine such as a knitting machine used in the production of a knit pile fabric. More particularly, the invention relates to a pattern control system used in the machine to create a predetermined pattern in the fabric being knitted.

In a typical knitting machine, two different colors of pile fibers in the form of rovings are drawn at variable rates into a device where the fibers are blended together to form the fabric in the pattern desired. The rates at which the two colors of fibers are drawn into the device are controlled by means programmed to actuate a feed unit for each of the colors of fibers. The feed units are driven by their own variable speed motors which are energized by output voltages of the programmed means to run at speeds proportional to the magnitudes of the output voltages. The running speeds of the motors, in turn, determine the rates the fibers are fed into the device.

The output voltages are created from a reference voltage produced by a tachometer which is driven by the device and the output voltages are varied in magnitude by the programmed means according to the pattern to be produced in the fabric. Accordingly, the fibers are fed into the device at relatively greater or lesser rates to produce the different color mixes for forming the various segments of the pattern in the fabric.

SUMMARY OF THE INVENTION The primary object of the present invention is to provide a textile machine of the above general character with a new and improved pattern control system which is much simpler than prior pattern control systems and which, in service use, eliminates detectable pattern flaws resulting from variations in the magnitude of the reference signal or voltage supplied to the programmed means by the tachometer. A more detailed object is to achieve the foregoing while also providing a pattern control system which is capable of being used to produce many more different patterns than was possible heretofore. In addition, a more specific object of the present invention is to construct the pattern control system so that less time is required and it is easier to change the pattern of the fabric being produced by the machine so as to reduce substantially downtime of the textile machine when changing patterns.

A further object is to achieve the foregoing through the provision of a novel arrangement for producing the output signals or voltages from the reference signal so that one of the output signals is an adjustable fraction of the reference signal while the other output signal is equal to the difference between the reference signal and the first output signal. In this manner, thecombined rate of feed of the two fibers is kept proportional to the speed of the device while changes in the color mix of the fibers are produced by adjusting only the first output signal.

The invention also resides in the provision of a potentiometer which is energized by the reference signal and is adjustable to produce the first output signal as a fraction of the reference signal and in the provision of an algebraic combining device which is coupled to receive the reference signal and the first output signal so as to produce the second output signal as the difference between the reference signal and the first output signal.

In addition, the invention resides in the provision of a drum programmer which controls the duration of each output signal independently of the reference signal so that the repetitions of the pattern in the fabric appear identical to each other regardless of variations in the magnitude of the reference signal.

Still further, the invention resides in the novel construction of the drum programmer and in the provision of a replaceable body within the programmer for quickly and easily changing the pattern in the fabric being produced by the textile machine.

These and other objects and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary elevational view of a textile machine embodying the novel features of the present invention.

FIG. 2 is an enlarged fragmentary cross-sectional view taken substantially along line 22 of FIG. 1.

FIG. 3 is an enlarged fragmentary cross-sectional view taken substantially along line 33 of FIG. 1.

FIG. 4 is an enlarged fragmentary view taken substantially along line 44 of FIG. 1.

FIG. 5 is an enlarged fragmentary cross-sectional view taken substantially along line 5--5 of FIG. 4.

FIG. 6 is a fragmentary view taken substantially along line 6-6 of FIG. 5.

FIG. 7 is a greatly enlarged, fragmentary crosssectional view taken substantially along line 77 of FIG. 5.

FIG. Sis a generalized schematic diagram of the electrical circuitry employed in the exemplary embodiment of the present invention.

FIG. 9 is a layout of a part of the drum programmer employed in the present invention to produce a fabric having a predetermined pattern.

FIG. 10 is a representation of a patterned fabric sample produced by the textile machine embodying the present invention. '7

DETAILED DESCRIPTION OF THE PREFERRED ENIBODIMENT two different colors of pile fibers in the form of rovings 29 and 30 into the fabric. Herein, the device comprises a ring gear 19 rotatably supported within a fixed head ring 20. Suitable gearing 21 connects the ring gear to a drive shaft 23 which in turn is driven by a motor 24 mounted on the frame so that the ring gear is turned at a predetermined speed within the head ring. Supported on the ring gear for movement therewith is a needle cylinder 25 (see FIG. 2) carrying a series of latch needles 26 which move vertically with respect to the cylinder upon riding over a cam (not shown) as the needle cylinder is rotated with the ring gear inside of the head ring. Mounted on the head ring at annularly spaced positions are eight carding heads 27 (only one being shown) through which the rovings 29 and 30 of pile fiber are fed onto the machine to be pulled in tufts into a knit backing 31 by the latch needles as an incident to knitting the backing. The latter is formed of a plurality of threads 33 fed from an equal number of supply spools (not shown) through tubes 34 located adjacent each of the carding heads. As the latch needles pass by the tubes, the threads are pulled from the lower ends of the tubes and are knitted into the fabric sleeve 16 by the action of the needles as they ride over the cam. At the same time, the needles pull tufts of pile from the carding heads and interloop the thread and tufts to knit the fabric sleeve.

Within each of the carding heads 27, the pile fibers from the two rovings 29 and 30 are mixed together to form a desired color for the fabric 16 being knitted. To distinguish the two rovings from each other, the roving 29 hereinafter will be referred to as the dark roving while the other roving 30 will be referred to as the light roving. It will be appreciated, however, that the two rovings may be of any selected colors or may even be the same color if such is desired. Moreover, because the carding heads are identical to each other, only one of the heads will be described in detail in order to avoid unnecessary repetition of description. Now, with reference to FIG. 2, the carding head is shown to include a main cylinder 35 fixed on a rotatable shaft 36 which is drivingly connected to the ring gear 19 so that the cylinder turns in relation to the speed at which the ring gear is being rotated. Secured to the periphery of the cylinder is a strip of card clothing 37 which includes a plurality of radially slanted wire teeth 39 extending outwardly from the cylinder to pull pile fibers from the rovings to catch on the cylinder as the latter turns with the shaft.

Mounted in the carding head 27 behind the cylinder 35 is a doffer roll 40 which is fixed on a second rotatable shaft 41. The latter also is connected drivingly with the ring gear 19 so as to rotate in relationship with the rotation of the ring gear but at a much faster speed than the speed of the main cylinder. Also wrapped around the periphery of the doffer roll is card clothing 43 which in this instance includes a plurality of outwardly extending teeth 44 whose outer ends are hooked in the direction of rotation of the roll to comb between the teeth 39 on the main cylinder. Accordingly, as the main cylinder and doffer roll are turned on their respective shafts, the pile fibers are combed from the main cylinder by the doffer roll and carried therewith for tufts of the fibers to be pulled from the doffer roll and interlooped with the thread 33 by the latch needles 26 as the fabric is being knitted.

As shown in FIG. 2, the dark roving 29 is fed onto the main cylinder 35 from a supply (not shown) adjacent the carding head 27 by means of a lower feed unit 45 including a series of pairs of drive rollers 48. The latter serve to pull the roving from the supply and flatten the roving into a fibrous web while at the same time stretching the roving longitudinally to thin out the web. This is accomplished by driving each successive pair of the drive rollers at a speed substantially faster than the next preceding pair of rollers. As the web of thinned fibers exit from the last pair of rollers 48, the web is picked up by the teeth 39 on the card clothing 37 of the rotating main cylinder to form a thin layer of fibers on the periphery of the main cylinder. Similarly, the light roving 30 is fed into the carding head by means of an upper feed unit 46 comprising a series of pairs of rollers 52 so that the light fibers of pile overlay the dark fibers on the main cylinder.

It will be appreciated that the speed at which the drive rollers 48 and 52 are rotated determines the relative rates at which the dark and light rovings 29 and 30 are being fed into the carding head 27 and, as a result, the various color mixes of the fibers for the different segments of the pattern in the fabric 16 being knitted. Accordingly, a pattern such as that shown on the piece of fabric illustrated in FIG. 10 may be produced by varying the feed rates of the two rovings in relation to each other for preselected periods of time. For instance, a dark stripe 47 is produced in the fabric by increasing the feed rate of dark roving 29 into the carding head over the feed rate of the light roving 30. The width a of the stripe, of course, depends upon the length of time over which the greater amount of dark roving is fed into the carding head while the color mix of the fibers comprising the stripe depends upon the difference in the relative feed rates of the two different colors of rovings. While the stripe 47 represents a relatively abrupt and large change between the relative rates at which the two rovings are being drawn into the carding head, the pattern also may be adjusted to gradually fade from one color mix into another by slowly making small changes in the relative feed rates of the rovings such as is represented by the area b in FIG. 10.

Herein, the drive rollers 48 and 52 of the feed units 45 and 46, respectively, are power rotated by suitable lower and upper motors 49 and 50 (see FIGS. 1 and 3) such as direct current variable speed motors. The speeds at which the motors run and, as a result, the speeds at which the rollers feed the rovings 29 and 30 into the carding head 27 are directly proportional to the voltages of two power signals E and E of means 51 (FIGS. 1, 4 and 8) programmed to produce the desired pattern in the fabric. The programmed means converts a reference signal in the form of a voltage E produced by a shaft tachometer generator 53 into the two power signals or voltages E and E The tachometer is driven by the device 17 through connection with the power shaft 23 of the main drive motor 24. Accordingly, the reference voltage produced by the tachometer is directly proportional to the speed of the device. Suitable means including power amplifiers 54 and 55 energize the motors 49 and 50, respectively, to run at speeds proportional to the magnitudes of the voltages E and E By utilizing the programmed means to selectively change the relative magnitudes of these voltages, the rovings 29 and 30 are fed into the carding head 27 at differing rates and are mixed together to produce the different color mixes needed for the various segments of the fabric pattern.

The present invention contemplates the provision of a greatly simplified pattern control system which enables the textile machine 15 to be used to produce a much wider variety of patterns in the fabric 16 and which virtually eliminates detectable pattern flaws in the fabric while also greatly simplifying and expediting the pattern changeover process for the machine. For these purposes, the power signal E is produced as an adjustable fraction of the reference signal E by selector means 61 receiving the reference signal from the tachometer 53. The power signal E is produced as the difference between the reference signal E and the power signal E byan algebraic combining device 52 coupled with the means for energizing the motor 50. By virtue of this arrangement, the combined rate of feed of the two rovings 29 and 30 remains proportional to the predetermined speed of the device 17 and the color mix of the blended fibers of the rovings is changeable by adjusting only the fraction produced by the selector means.

In the present instance, the selector means 61 is in the form of a potentiometer (FIG. 8) energized by the reference signal or voltage E and comprising a plurality of resistors 75, herein sixteen, connected in series with each other. The setting of the potentiometer is adjusted to pick off different fractions of the reference voltage by selectively closing 'and opening switches 59 to increase or decrease the resistance of the potentiometer. By selectively closing one of the switches, the power signal or voltage E is routed to the means for energizing the motor 49. Herein, this means includes an operational amplifier 63 which, by itself, has a very high open loop gain. A resistor R; is connected to create a negative feedback by transmitting an output signal or voltage E of the amplifier of the subtractive or input terminal 63a. As a result, the output voltage appears as a transfer function of the input power voltage E A but with opposite polarity.

The input voltage E is connected through a resistor R,, so that the output voltage E is weighted not only according to the magnitude of the voltage applied to such resistor, but also according to the ratio of the feedback resistor R; to the input resistance. Thus, the amplifier 63 in FIG. 8 operates to produce the output signal which varies according to the equation:

. where the negative sign on the right indicates that the output signal is negative in polarity relative to the polarity of the input voltage E A due to the inversion which results in the amplifier 63 for a signal applied to the subtractive input terminal 63a.

The reference voltage E also is routed through the algebraic combining device 52 (FIG. 8) which, herein, includes a second operational amplifier 64 similar to the amplifier 63. The voltage is transmitted through an input resistance R,, to an additive input terminal 64a of the operational amplifier 64 so that the magnitude of the portion of the input power signal or voltage E applied to the amplifier through the resistance R, is equal to E (R /R In addition, the output signal E from amplifier 63 is transferred through a resistance R, to the input terminal 64a in an additive and subtractive sense as a second portion of the voltage E whose magnitude is E R,/R,). Then from inspection, the transfer function of the amplifier 64 is set forth by equation:

EH0 n I/ b) EAO I t) In the exemplary form of the invention, the gain in each amplifier is a unity so that equation (1) then becomes equation (2) becomes Addingequations (3) and (5) produces the equation:

EAO EH0 ER.

Thus, it is seen that as the magnitude of output voltage of one of the amplifiers 63 or 64 increases or decreases there is a corresponding decrease or increase in the magnitude of the output voltage of the other amplifier so that the combined rate of feed of the two rovings 29 and 30 remains proportional to the speed of the device 17. Moreover, it will be appreciated that, the blend of the fibers of the rovings is changeable by adjusting only the voltage E produced by the potentiometer 61.

Preferably, the opening and closing of the switches 59 to change the voltage E A is accomplished by the programmed means 51 which is in the form of a drum programmer (see FIGS. 1 and 4 through 7). Advantageously, the drum programmer 51 is operated independently of the reference voltage E so that repetitions of the pattern in the fabric 16 appear identical to each other regardless of variations which may occur in the magnitude of the reference voltage E during normal operation of the the textile machine 15. As shown in FIG. 4, the programmer includes an upright rotatable drum 56 supported by a platform 67 attached to one side of the machine and carrying a plurality of cam strips 57. As the drum is rotated, the cam strips selectively close the switches 59 to change the magnitude of the voltage E Herein, the switches are mounted on two vertically extending posts 77 (see FIG. 4) fixed to the platform adjacent the drum. As shown in FIGS. 6 and 7, each switch comprises a spring arm 76 carrying one of the contacts 74 of the switch and is biased normally away from the other contact 73 of the switch. When engaged by the cam strips, the spring arms are moved to close the contacts of the switches thereby completing the circuit between the potentiometer 61 and the first operational amplifier 63.

Advantageously, the drum 56 of the exemplary programmer 51 is constructed in a novel fashion to enable the pattern being produced by the machine 15 to be changed quickly and easily so as to reduce substantially the downtime otherwise required of the machine to change patterns. To these ends, the drum comprises a generally cylindrical body 60 (FIG. 5) upon the outside of which is attached the cam strips 57. A circular bottom plate 81 is secured to the lower end portion of the body and is recessed upwardly from the lower edge 83. To secure the drum to the gear 66 for rotation by the motor 65, a circular base 84 is fastened to the gear such as by screws 85 and includes a peripheral annular groove 86 receiving the lower edge portion of the body so the latter is telescoped over the upper end of the base and into the recess to keep from moving laterally relative to the base during rotation. Herein, the drum is fastened to the base by means of screws 87 extending through the bottom plate and into the base. A circular lid 89 is secured to the top of the drum by an axially extending rod 90 which is threaded into the plate and a wing nut 91 is tightened against the lid on the upper end of the rod. With this arrangement, the drum may be removed quickly and easily from the base and replaced with another drum carrying a different pattern of cam strips so as to change the pattern in the fabric to be produced by the machine.

A stepping motor 65 bolted to the underside of the platform 67 drives the drum 56 independently of the reference voltage E so that the speed at which the drum is rotated is related directly to the size of the pattern, that is, the width of each of the various stripes in the pattern. Herein, the drum is connected to the motor by way of gears 66 and 71, respectively, secured to the drum and the drive shaft 70 of the motor so the drum is rotated upon energization of the motor. A suitable regulator 72 (FIGS. and 8) such as the Slo-Syn Translator manufactured by Superior Electric Co. of Bristol, Connecticut is used to convert a l 10 A.C. voltage from a conventional source 80 into a stepping voltage operable to power the stepping motor 65. The regulator provides suitable controls which by turning a knob 81 may be adjusted to set the speed of the stepping motor as desired to either lengthen or shorten the pattern being produced by the programmer.

To compensate for the time required for the textile machine to build up to normal running speed when started from a dead stop, the motor 65 is kept from being energized until the reference voltage E reaches a certain threshold value indicating the machine has reached a certain threshold speed. In the present instance, this is accomplished by means of a switching transistor 93 (see FIG. 8) connected to receive the voltage E and operable when the voltage E reaches approximately one-half of its normal value to actuate a solenoid 94 to close a switch 95 coupled between voltage source 80 and the regulator 72. Advantageously, the foregoing arrangement avoids the formation of any detectable pattern flaws which otherwise may result from the difference in time required for the drum 56 and the machine 15 to build up to their normal operating speeds.

As shown in FIG. 9, the drum layout of the cam strips 57 are arranged to close the switches 59 one at a time to pick off the desired magnitude of voltage E Herein, closing of the upper switches 59 produces higher magnitudes of voltage E so that the motor 49 runs faster than the motor 50 thereby feeding a greater amount of dark fibers into the device 17 to produce a darker color mix of fibers. Similarly, closing of the lower switches produces lower magnitudes of voltages E so the motor 49 runs slower than the speed of the motor 50 to produce a lighter color mix of fibers. The length of time which the switches are closed for each magnitude of the voltage E of course, determines the width of the stripe being produced in the fabric by the particular color mix associated with each of those magnitudes. In turn, the length time which the switches are closed depends upon the length of the various cam strips 57 in the direction of rotation of the drum 56 and the speed at which the drum is rotated. Accordingly, by placing the cam strips on the drum as shown in FIG. 9 to selectively close the switches, a pattern such as that shown in FIG. 10 may be formed in the fabric 16 being produced by the machine 15.

In particular, with respect to FIGS. 9 and 10, the cam strip 57a closes the uppermost switch 59 so the motor 49 runs at full speed. Because the amplifier 63 is of unity gain, the output signal E is of the same magnitude as but of reversed polarity to the reference signal E Accordingly, when the signal E is combined with the reference signal at the input terminal 64a of the second operational amplifier 64, the two signals cancel each other out so that the magnitude of the voltage E is zero and the motor fails to receive any power. Because the switches are each spring urged into their open positions, as the end of the cam strip 57a is rotated past the uppermost switch, the latter opens to break the connection between the amplifier 63 and the potentiometer 61. At this point in the pattern illustrated, no other switches are closed so that the magnitude of the voltage E goes to zero and the motor 49 fails to receive any power. On the other hand, the output voltage E becomes equal in magnitude to but reversed in polarity from the reference voltage E so there is an abrupt change from feeding only dark pile fibers into the carding head 27 to feeding in only light pile fibers. This, of course, causes a change from producing the dark stripe 47a in the fabric to the light stripe 48.

As the drum 56 continues to rotate, the upwardly slanted cam strip 57b engages and closes the lowermost switch 59 to produce a mix of light and dark fibers and, thereafter, the switches are consecutively opened and closed upon progressing upwardly along the cam strip 57b until the uppermost switch again is closed. Thus, the magnitude of the output voltage E gradually increases while the magnitude of the output voltage E gradually decreases in equal increments. This produces a slow increase in the mixture of dark fibers relative to the light fibers so the light stripe 48 gradually fades into a dark line stripe 52. Further rotation of the drum brings the downwardly slanted cam strip 57c into en gagement with the switches to reverse the fading from dark to light and to form a second light stripe 48 until the uppermost switch is closed again by the cam strip 57a to repeat the pattern.

By selectively locating different cam strips 57 of various length on the drum in different positions, practically an infinite variety of patterns may be produced in the fabric 16 being knitted. Moreover, the lengths of the patterns either may be increased or decreased as desired by adjustment of the speed of rotation of the drum 56 by turning the knob 81 on the regulator 72. Still further, because the drum is power rotated independently of the magnitude of the reference voltage E the various segments of the patterns are reproduced accurately to virtually eliminate any detectable flaws in the pattern being produced regardless of variations in the magnitude of the reference voltage E In view of the foregoing, it will be appreciated that the pattern control system of the present invention is much simpler in construction than prior similar systems and, in service use, virtually eliminates detectable pattern flaws in the fabric 16 while also providing a greatly increased capacity for producing different patterns in the fabric. To these ends, the potentiometer 61 produces the voltage E A which controls the motor speed of the first feed unit 45 as an adjustable fraction of the reference voltage E and the algebraic combining device 52 in the form of the operational amplifier 64 receives both the reference voltage and the output voltage E of the first operational amplifier 63 to produce the output voltage E which is equal to the difference of the reference voltage and the output voltage E The magnitude of the output voltage E of course, determines the speed of the drive motor 50 of the second feed unit 46 to provide the appropriate color mix for the segment of the pattern being produced in the fabric. Advantageously, adjustment of the potentiometer is achieved through the use of the drum programmer 51 including the cam strips 57 serving to close the switches 59 so the length of time any one magnitude of the voltage E is produced is determined independently of the magnitude of the reference voltage E by the speed of rotation of the drum 56. Thus, the formation of detectable flaws in the pattern of the fabric which otherwise may result from variations in the magnitude of the reference voltage E is avoided. Moreover, because the drum may be removed and replaced quickly and easily, the downtime previously required to change patterns in the machine is reduced substantially.

We claim as our invention:

1. In a textile machine adapted to form fabric by mixing fibers of at least two different colors, the combination comprising a device driven at a predetermined speed for blending and forming the two colors of fibers into a fabric, first and second feed units driven by first and second motors for transferring the two respective colors of fibers into said device at rates respectively proportional to the speeds of those motors, means for producing a first signal proportional to the speed of said device, selector means for producing a second sig nal which is an adjustable fraction of said first signal, means for energizing said first motor to run at a speed proportional to said second signal, and means for energizing said second motor to run at a speed proportional to the difference between said first and second signals, whereby the combined rate of feed of said two colors of fibers into said device remains proportional to the speed of said device and the mix of the two blended colors of fibers is changeable by adjusting the fraction produced by said selector means.

2. In a textile machine adapted to form fabric by mixing fibers of at least two different colors, the combination comprising a device driven at a predetermined speed for blending and forming the two colors of fibers into a fabric, first and second feed units coupled to said device for transferring the two respective colors of fibers into it, first and second motors respectively driving said first and second feed units to feed the two respective colors of fibers at rates corresponding to the respective motor speeds, a tachometer driven by said device and producing a first voltage proportional to said predetermined speed, a potentiometer energized by said first voltage and adjustable to produce a second voltage which is a selectable fraction of the first, means responsive to said second voltage for energizing said first motor to run at a speed proportional to that voltage, an algebraic combining device coupled to receive said first and second voltages and to produce a third voltage equal to their difference, and means responsive to said third voltage for energizing said second motor to run at a speed proportional to that voltage.

3. A textile machine as defined by claim 2 wherein said means responsive to said second voltage includes a first operational amplifier.

4. A textile machine as defined by claim 3 wherein said algebraic combining device includes a second operational amplifier.

5. A textile machine as defined by claim 4 including means operable independently of said first voltage for adjusting said potentiometer to produce said second voltage for a predetermined period of time corresponding to the width of the segment of the pattern being formed.

6. A textile machine as defined by claim 5 wherein said potentiometer adjusting means includes means selectively movable to complete an electrical connection between said potentiometer and said first operational amplifier, and cam means for selectively engaging and moving said movable means to pick off said second voltage from said first voltage.

7. A textile machine as defined by claim 6 including a third motor energized independently of said first voltage to move said cam means selectively into engagement with said movable means so as to keep variations in the magnitude in said first voltage from affecting the widths of the segments of the pattern being produced in the fabric.

8. A textile machine as defined by claim 7 wherein said potentiometer includes a plurality of resistors connected together in series.

9. A textile machine as defined by claim 8 wherein said movable means comprises a plurality of switches associated with said resistors, said switches being spring urged into open positions to be closed selectively to complete a circuit to said first amplifier through a selected number of said resistors and thereby pick off said second voltage from said first voltage.

10. A textile machine as defined by claim 7 wherein said cam means comprises a rotatable drum drivingly connected to said third motor, a plurality of cam strips attached to the outer surface of said drum to selectively close said switches as said drum is rotated.

11. A textile machine as defined by claim 10 including means to control the operating speed of said third motor so as to thereby'control the speed of rotation of said drum.

12. A textile machine as defined by claim 11 further including means operable to delay energization of said third motor when said textile machine is started until said device approaches its predetermined speed.

13. A textile machine as defined by claim 12 wherein said delaying means comprises a switching transistor responsive to the magnitude of said first voltage to cause said third motor to be energized as said firt voltage approaches one-half of its magnitude when said device is operating at said predetermined speed.

14. A textile machine as defined by claim 10 wherein said drum includes a replaceable, generally cylindrical body carrying said cam strips.

15. A textile machine as defined by claim 14 wherein said drum further includes a base carrying said body and rotated by said third motor so the cam strips engage said switches.

16. A textile machine as defined by claim 15 wherein said body includes a bottom plate fastened to said base, a lid supported on said body opposite said plate, a threaded rod telescoped through said lid and connected to said plate, a nut threaded on the upper end of said rod to secure said lid on the body.

17. In a textile machine adapted to form a patterned fabric by mixing fibers of at least two different colors, the combination comprising a device driven at a predetermined speed for blending and forming the two colors of fibers into the fabric, first and second feed units coupledto said device for transferring the two respective colors of fibers into said device, first and second motors respectively driving said first and second feed units at rates corresponding to the respective motor speeds so that, as the latter are varied with respect to each other, the color mix of the fibers is changed to form the different segments of the pattern in the fabric, a tachometer driven by said device and producing a reference voltage proportional to said predetermined speed, a potentiometer energized by said reference voltage and adjustable to produce a first input voltage which is a selectable fraction of the reference voltage, a first operational amplifier responsive to said input voltage to produce a first output voltage for energizing said first motor to run at a speed proportional to said output voltage, means combining said reference voltage and said first output voltage to produce a second input voltage equal to their difference, and a second operational amplifier responsive to said second input voltage to produce a second output voltage for energizing said second motor, the sum of said first and second output voltages being proportional to said reference signal.

18. In a textile machine adapted to form a patterned fabric by mixing fibers of at least two different colors, the combination comprising a device driven at a predetermined speed for blending the two colors of fibers together to form the different color mixes of the pattern in the fabric and for forming the fabric, first and second feed units coupled to said device for transferring the two respective colors of fibers into it, first and second variable speed motors respectively driving said first and second feed units to feed the two respective colors of fibers into said device at rates corresponding to the respective motor speeds so that, as the latter are varied with respect to each other, the color mix of the fibers is changed to form the different segments of the pattern in the fabric, a tachometer driven by said device and producing a reference voltage proportional to said predetermined speed, a potentiometer energized by said reference voltage, means operable independently of said reference voltage for adjusting said potentiometer for a predetermined period of time corresponding to the width of the segment of the pattern being formed to produce a first input voltage which is a selectable fraction of said reference voltage, a first operational amplifier responsive to said input voltage to produce a first output voltage for energizing said first motor to run at a speed proportional to said output voltage, means combining said reference voltage and said first output voltage to produce a second input voltage equal to their difference, and a second operational amplifier responsive to said second output voltage for energizing said second motor, the sum of said first and second output voltages being proportional to said reference signal. l 

1. In a textile machine adapted to form fabric by mixing fibers of at least two different colors, the combination comprising a device driven at a predetermined speed for blending and forming the two colors of fibers into a fabric, first and second feed units driven by first and second motors for transferring the two respective colors of fibers into said device at rates respectively proportional to the speeds of those motors, means for producing a first signal proportional to the speed of said device, selector means for producing a second signal which is an adjustable fraction of said first signal, means for energizing said first motor to run at a speed proportional to said second signal, and means for energizing said second motor to run at a speed proportional to the difference between said first and second signals, whereby the combined rate of feed of said two colors of fibers into said device remains proportional to the speed of said device and the mix of the two blended colors of fibers is changeable by adjusting the fraction produced by said selector means.
 2. In a textile machine adapted to form fabric by mixing fibers of at least two different colors, the combination comprising a device driven at a predetermined speed for blending and forming the two colors of fibers into a fabric, first and second feed units coupled to said device for transferring the two respective colors of fibers into it, first and second motors respectively driving said first and second feed units to feed the two respective colors of fibers at rates corresponding to the respective motor speeds, a tachometer driven by said device and producing a first voltage proportional to said predetermined speed, a potentiometer energized by said first voltage and adjustable to produce a second voltage which is a selectable fraction of the first, means responsive to said second voltage for energizing said first motor to run at a speed proportional to that voltage, an algebraic combining device coupled to receive said first and second voltages and to produce a third voltage equal to their difference, and means responsive to said third voltage for energizing said second motor to run at a speed proportional to that voltage.
 3. A textile machine as defined by claim 2 wherein said means responsive to said second voltage includes a first operational amplifier.
 4. A textile machine as defined by claim 3 wherein said algebraic combining device includes a second operational amplifier.
 5. A textile machine as defined by claim 4 including means operable independently of said first voltage for adjusting said potentiometer to produce said second voltage for a predetermined period of time corresponding to the width of the segment of the pattern being formed.
 6. A textile machine as defined by claim 5 wherein said potentiometer adjusting means includes means selectively movable to complete an electrical connection between said potentiometer and said first operational amplifier, and cam means for selectively engaging and moving said movable means to pick off said second voltage from said first voltage.
 7. A textile machine as defined by claim 6 including a third motor energized independently of said first voltage to move said cam means selectively into engagement with said movable means so as to keep variations in the magnitude in said first voltage from affecting the widths of the segments of the pattern being produced in the fabric.
 8. A textile machine as defined by claim 7 wherein said potentiometer includes a plurality of resistors connected together in series.
 9. A textile machine as defined by claim 8 wherein said movable means comprises a plurality of switches associated with said resistors, said switches being spring urged into open positions to be closed selectively to complete a circuit to said first amplifier through a selected number of said resistors and thereby pick off said second voltage from said first voltage.
 10. A textile machine as defined by claim 7 wherein said cam means comprises a rotatable drum drivingly connected to said third motor, a plurality of cam strips attached to the outer surface of said drum to selectively close said switches as said drum is rotated.
 11. A textile machine as defined by claim 10 including means to control the operating speed of said third motor so as to thereby control the speed of rotation of said drum.
 12. A textile machine as defined by claim 11 further including means operable to delay energization of said third motor when said textile machine is started until said device approaches its predetermined speed.
 13. A textile machine as defined by claim 12 wherein said delaying means comprises a switching transistor responsive to the magnitude of said first voltage to cause said third motor to be energized as said firt voltage approaches one-half of its magnitude when said device is operating at said predetermined speed.
 14. A textile machine as defined by claim 10 wherein said drum includes a replaceable, generally cylindrical body carrying said cam strips.
 15. A textile machine as defined by claim 14 wherein said drum further includes a base carrying said body and rotated by said third motor so the cam strips engage said switches.
 16. A textile machine as defined by claim 15 wherein said body includes a bottom plate fastened to said base, a lid suppoRted on said body opposite said plate, a threaded rod telescoped through said lid and connected to said plate, a nut threaded on the upper end of said rod to secure said lid on the body.
 17. In a textile machine adapted to form a patterned fabric by mixing fibers of at least two different colors, the combination comprising a device driven at a predetermined speed for blending and forming the two colors of fibers into the fabric, first and second feed units coupled to said device for transferring the two respective colors of fibers into said device, first and second motors respectively driving said first and second feed units at rates corresponding to the respective motor speeds so that, as the latter are varied with respect to each other, the color mix of the fibers is changed to form the different segments of the pattern in the fabric, a tachometer driven by said device and producing a reference voltage proportional to said predetermined speed, a potentiometer energized by said reference voltage and adjustable to produce a first input voltage which is a selectable fraction of the reference voltage, a first operational amplifier responsive to said input voltage to produce a first output voltage for energizing said first motor to run at a speed proportional to said output voltage, means combining said reference voltage and said first output voltage to produce a second input voltage equal to their difference, and a second operational amplifier responsive to said second input voltage to produce a second output voltage for energizing said second motor, the sum of said first and second output voltages being proportional to said reference signal.
 18. In a textile machine adapted to form a patterned fabric by mixing fibers of at least two different colors, the combination comprising a device driven at a predetermined speed for blending the two colors of fibers together to form the different color mixes of the pattern in the fabric and for forming the fabric, first and second feed units coupled to said device for transferring the two respective colors of fibers into it, first and second variable speed motors respectively driving said first and second feed units to feed the two respective colors of fibers into said device at rates corresponding to the respective motor speeds so that, as the latter are varied with respect to each other, the color mix of the fibers is changed to form the different segments of the pattern in the fabric, a tachometer driven by said device and producing a reference voltage proportional to said predetermined speed, a potentiometer energized by said reference voltage, means operable independently of said reference voltage for adjusting said potentiometer for a predetermined period of time corresponding to the width of the segment of the pattern being formed to produce a first input voltage which is a selectable fraction of said reference voltage, a first operational amplifier responsive to said input voltage to produce a first output voltage for energizing said first motor to run at a speed proportional to said output voltage, means combining said reference voltage and said first output voltage to produce a second input voltage equal to their difference, and a second operational amplifier responsive to said second output voltage for energizing said second motor, the sum of said first and second output voltages being proportional to said reference signal. 